Nanotube film structure

ABSTRACT

The disclosure relates to a nanotube film structure. The nanotube film structure includes at least one nanotube film. The at least one nanotube film includes a plurality of nanotubes orderly arranged and combined with each other by ionic bonds. The nanotube film is fabricated by using the template of carbon nanotube film. The carbon nanotube film is drawn from supper aligned carbon nanotube array and includes a plurality of carbon nanotubes joined end to end.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.201410115685.4 filed on Mar. 26, 2014 in the China Intellectual PropertyOffice, the contents of which are incorporated by reference herein.

FIELD

The subject matter herein generally relates to nanotube film and methodsfor making the same.

BACKGROUND

Many novel properties are beyond traditional theories of materialscience and properties when the materials are at a nanoscale.Nanomaterial has become representative of modern science and technologyand future research because of their distinct catalytic reaction,electrical, physical, magnetic, and luminescent properties. Many methodshave been developed to manufacture nanomaterial, such as spontaneousgrowth, template-based synthesis, electro-spinning, and lithography.

A carbon nanotube film has been fabricated by drawing from a supperaligned carbon nanotube array. The carbon nanotube film includes aplurality of carbon nanotubes joined end to end along the drawingdirection. However, because each of the plurality of carbon nanotubeshas a sealed end, the bonding force at joint between adjacent carbonnanotubes is only van der Waals force. Thus, the strength of the carbonnanotube film is relatively weak.

What is needed, therefore, is to provide a nanotube film and a methodfor solving the problem discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof example only, with reference to the attached figures, wherein:

FIG. 1 is a flowchart of one embodiment of a method for making ananotube film.

FIG. 2 is a Scanning Electron Microscope (SEM) image of a carbonnanotube film.

FIG. 3 is a schematic structural view of a carbon nanotube segment ofthe carbon nanotube film of FIG. 2.

FIG. 4 is a schematic structural view of the carbon nanotube film ofFIG. 2.

FIG. 5 is a partially enlarged view of FIG. 4.

FIG. 6 is an SEM image of two cross-stacked carbon nanotube films.

FIG. 7 is schematic view of one embodiment of a method for stretchingthe carbon nanotube film of FIG. 4.

FIG. 8 is an SEM image of a stretched carbon nanotube film made bymethod of FIG. 7.

FIG. 9 is an SEM image of one embodiment of an alumina (Al₂O₃) layerdeposited on a pristine carbon nanotube film by atomic layer deposition(ALD).

FIGS. 10A-10C show transmission electron microscope (TEM) images ofalumina layers with different thickness deposited on pristine carbonnanotube films by atomic layer deposition.

FIG. 11 is an SEM image of one embodiment of an alumina layer depositedon a carbon nanotube film treated with oxygen plasma by atomic layerdeposition.

FIGS. 12A-12E show TEM images of alumina layers with different thicknessdeposited on carbon nanotube films treated with oxygen plasma by atomiclayer deposition.

FIG. 13 is a transmission electron microscope (TEM) image of oneembodiment of a carbon nanotube film treated by carbon accumulation.

FIG. 14 is an SEM image of one embodiment of an alumina layer depositedon a pristine carbon nanotube film by atomic layer deposition.

FIG. 15 is an SEM image of one embodiment of an alumina layer depositedon a carbon nanotube film treated by carbon accumulation by atomic layerdeposition.

FIG. 16 is an SEM image of one embodiment of a single alumina nanotubefilm.

FIG. 17 is an SEM image of one embodiment of two cross-stacked aluminananotube films.

FIG. 18 is a photo of an alumina nanotube film.

FIG. 19 is a schematic structural view of one embodiment of a singlenanotube film.

FIG. 20 is a schematic structural view of one embodiment of a nanotubeof the nanotube film of FIG. 19.

FIG. 21 is a schematic structural view of one embodiment of twocross-stacked nanotube films.

FIG. 22 shows a relationship between a load and a strain of thecross-stacked alumina nanotube film made by template of a pristinecarbon nanotube film.

FIG. 23 shows a relationship between a load and a strain of thecross-stacked alumina nanotube film made by template of a carbonnanotube film treated with oxygen plasma.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures and components have notbeen described in detail so as not to obscure the related relevantfeature being described. The drawings are not necessarily to scale andthe proportions of certain parts may be exaggerated to better illustratedetails and features. The description is not to be considered aslimiting the scope of the embodiments described herein.

Several definitions that apply throughout this disclosure will now bepresented.

The term “coupled” is defined as connected, whether directly orindirectly through intervening components, and is not necessarilylimited to physical connections. The connection can be such that theobjects are permanently connected or releasably connected. The term“outside” refers to a region that is beyond the outermost confines of aphysical object. The term “inside” indicates that at least a portion ofa region is partially contained within a boundary formed by the object.The term “substantially” is defined to be essentially conforming to theparticular dimension, shape or other word that substantially modifies,such that the component need not be exact. For example, substantiallycylindrical means that the object resembles a cylinder, but can have oneor more deviations from a true cylinder. The term “comprising” means“including, but not necessarily limited to”; it specifically indicatesopen-ended inclusion or membership in a so-described combination, group,series and the like. It should be noted that references to “an” or “one”embodiment in this disclosure are not necessarily to the sameembodiment, and such references mean at least one.

References will now be made to the drawings to describe, in detail,various embodiments of the present nanotube film and methods for makingthe same.

Referring to FIG. 1, a method for making a nanotube film 114 of oneembodiment includes the following steps:

-   -   step (S10), providing a free standing carbon nanotube film 100,        wherein the carbon nanotube film 100 includes a plurality of        carbon nanotubes 104 orderly arranged and combined with each        other via van der Waals force to form a plurality of apertures        105 extending along a length direction of the plurality of        carbon nanotubes 104;    -   step (S20), inducing defects on surfaces of the plurality of        carbon nanotubes 104;    -   step (S30), growing a nano-material layer 110 on the surfaces of        the plurality of carbon nanotubes 104 by atomic layer        deposition;    -   step (S40), obtaining a free-standing nanotube film 114 by        removing the carbon nanotube film 100 by annealing, wherein        nanotube film 114 includes a plurality of nanotubes 112 orderly        arranged and combined with each other;

In step (S10), the carbon nanotube film 100 is drawn from a carbonnanotube array. Referring to FIGS. 2-5, the carbon nanotube film 100 isa substantially pure structure consisting of a plurality of carbonnanotubes 104, 106, with few impurities and chemical functional groups.The carbon nanotube film 100 is a free-standing structure. The term“free-standing structure” includes that the carbon nanotube film 100 cansustain the weight of itself when it is hoisted by a portion thereofwithout any significant damage to its structural integrity. Thus, thecarbon nanotube film 100 can be suspended by two spaced supports. Themajority of carbon nanotubes 104 of the carbon nanotube film 100 arejoined end-to-end along a length direction of the carbon nanotubes 104by van der Waals force therebetween so that the carbon nanotube film 10is a free-standing structure. The carbon nanotubes 104, 106 of thecarbon nanotube film 100 can be single-walled, double-walled, ormulti-walled carbon nanotubes. The diameter of the single-walled carbonnanotubes can be in a range from about 0.5 nm to about 50 nm. Thediameter of the double-walled carbon nanotubes can be in a range fromabout 1.0 nm to about 50 nm. The diameter of the multi-walled carbonnanotubes can be in a range from about 1.5 nm to about 50 nm.

The carbon nanotubes 104, 106 of the carbon nanotube film 100 areoriented along a preferred orientation. That is, the majority of carbonnanotubes 104 of the carbon nanotube film 100 are arranged tosubstantially extend along the same direction and in parallel with thesurface of the carbon nanotube film 100. Each adjacent two of themajority of carbon nanotubes 104 are joined end-to-end by van der Waalsforce therebetween along the length direction. A minority of dispersedcarbon nanotubes 106 of the carbon nanotube film 100 may be located andarranged randomly. However, the minority of dispersed carbon nanotubes106 have little effect on the properties of the carbon nanotube film 100and the arrangement of the majority of carbon nanotubes 104 of thecarbon nanotube film 100. The majority of carbon nanotubes 104 are notabsolutely form a direct line and extend along the axial direction, someof them may be curved and in contact with each other in microcosm. Somevariations can occur in the carbon nanotube film 100.

Referring to FIG. 3, the carbon nanotube film 100 includes a pluralityof successively oriented carbon nanotube segments 108, joined end-to-endby van der Waals force therebetween. Each carbon nanotube segment 108includes a plurality of carbon nanotubes 104 parallel to each other, andcombined by van der Waals force therebetween. A thickness, length andshape of the carbon nanotube segment 108 are not limited. A thickness ofthe carbon nanotube film 100 can range from about 0.5 nanometers toabout 100 micrometers, such as 10 nanometers, 50 nanometers, 200nanometers, 500 nanometers, 1 micrometer, 10 micrometers, or 50micrometers.

Referring to FIGS. 4-5, the majority of carbon nanotubes 104 of thecarbon nanotube film 100 are arranged to substantially extend along thesame direction to form a plurality of carbon nanotube wires 102substantially parallel with each other. The minority of carbon nanotubes106 are randomly dispersed on and in direct contact with the pluralityof carbon nanotube wires 102. The extending direction of the majority ofcarbon nanotubes 104 is defined as D1, and a direction perpendicularwith D1 and parallel with the carbon nanotube film 100 is defined as D2.The carbon nanotubes 104 of each carbon nanotube wire 102 are joinedend-to-end along D1, and substantially parallel and combined with eachother along D1. The plurality of apertures 105 are defined betweenadjacent two of the plurality of carbon nanotube wires 102 or theplurality of carbon nanotubes 104.

The carbon nanotube film 100 is stretchable along D2. When the carbonnanotube film 100 is stretched along D2, the carbon nanotube film 100can maintain its film structure. A distance between adjacent two of theplurality of carbon nanotube wires 102 will be changed according to thedeformation of the carbon nanotube film 100 along D2. The distancebetween adjacent two of the plurality of carbon nanotube wires 102 canbe in a range from about 0 micrometers to about 50 micrometers. Theratio of quantity or quality between the majority of carbon nanotubes104 and the minority of dispersed carbon nanotubes 106 can be greaterthan or equal to 2:1 and less than or equal to about 6:1. The more theminority of dispersed carbon nanotubes 106, the greater the maximumdeformation of the carbon nanotube film 100 along D2. The maximumdeformation of the carbon nanotube film 100 along D2 can be about 300%.In one embodiment, the ratio of quantity between the majority of carbonnanotubes 104 and the minority of dispersed carbon nanotubes 106 isabout 4:1.

The carbon nanotube film 100 can be made by following substeps:

-   -   step (S100), providing a carbon nanotube array on a substrate;        and    -   step (S102), drawing out the carbon nanotube film 100 from the        carbon nanotube array by using a tool.

In step (S100), the carbon nanotube array includes a plurality of carbonnanotubes that are parallel to each other and substantiallyperpendicular to the substrate. The height of the plurality of carbonnanotubes can be in a range from about 50 micrometers to 900micrometers. The carbon nanotube array can be formed by the substeps of:step (S1001) providing a substantially flat and smooth substrate; step(S1002) forming a catalyst layer on the substrate; step (S1003)annealing the substrate with the catalyst layer in air at a temperatureapproximately ranging from 700° C. to 900° C. for about 30 minutes to 90minutes; step (S1004) heating the substrate with the catalyst layer to atemperature approximately ranging from 500° C. to 740° C. in a furnacewith a protective gas therein; and step (S1005) supplying a carbonsource gas to the furnace for about 5 minutes to 30 minutes and growingthe carbon nanotube array on the substrate.

In step (S1001), the substrate can be a P-type silicon wafer, a N-typesilicon wafer, or a silicon wafer with a film of silicon dioxidethereon. A 4-inch P-type silicon wafer is used as the substrate. In step(S1002), the catalyst can be made of iron (Fe), cobalt (Co), nickel(Ni), or any alloy thereof. In step (S1003), the protective gas can bemade up of at least one of nitrogen (N₂), ammonia (NH₃), and a noblegas. In step (S1005), the carbon source gas can be a hydrocarbon gas,such as ethylene (C₂H₄), methane (CH₄), acetylene (C₂H₂), ethane (C₂H₆),or any combination thereof. The carbon nanotube array formed under theabove conditions is essentially free of impurities, such as carbonaceousor residual catalyst particles.

In step (S102), the drawing out the carbon nanotube film 100 includesthe substeps of: step (S1021) selecting one or more of carbon nanotubesin a predetermined width from the carbon nanotube array; and step(S1022) drawing the selected carbon nanotubes to form nanotube segmentsat an even and uniform speed to achieve the carbon nanotube film 100.

In step (S1021), the carbon nanotubes having a predetermined width canbe selected by using an adhesive tape, such as the tool, to contact thesuper-aligned array. In step (S1022), the drawing direction issubstantially perpendicular to the growing direction of the carbonnanotube array. Each carbon nanotube segment includes a plurality ofcarbon nanotubes parallel to each other.

In one embodiment, during the drawing process, as the initial carbonnanotube segments are drawn out, other carbon nanotube segments are alsodrawn out end-to-end due to van der Waals force between ends of adjacentsegments. This process of drawing helps provide a continuous and uniformcarbon nanotube film 100 having a predetermined width can be formed.

The width of the carbon nanotube film 100 depends on a size of thecarbon nanotube array. The length of the carbon nanotube film 100 can bearbitrarily set as desired. In one useful embodiment, when the substrateis a 4-inch P-type silicon wafer, the width of the carbon nanotube film100 can be in a range from about 0.01 centimeters to about 10centimeters. The thickness of the carbon nanotube film 100 can be in arange from about 0.5 nanometers to about 10 micrometers.

Furthermore, at least two carbon nanotube films 100 can be stacked witheach other or two or more carbon nanotube films 100 can be locatedcoplanarly and combined by only the van der Waals force therebetween. Asshown in FIG. 6, two carbon nanotube films 100 are stacked with eachother, and the majority of carbon nanotubes 104 of the two carbonnanotube films 100 are substantially perpendicular with each other.

Furthermore, in one embodiment, step (S10) further includes stretchingthe carbon nanotube film 100 along D2 so that the apertures 105 havelarger width. As shown in FIG. 7, the stretching the carbon nanotubefilm 100 includes: fixing two opposite sides of the carbon nanotube film100 on two spaced elastic supporters 200 so that a portion of the carbonnanotube film 100 are suspended between the two elastic supporters 200,wherein two elastic supporters 200 are parallel with each other andextend along D2; stretching the two elastic supporters 200 along D2 toobtain a stretched carbon nanotube film. As shown in FIG. 8, thestretched carbon nanotube film has increased apertures. The two elasticsupporters 200 can be elastic rubber, springs, or elastic bands. Thespeed of stretching the two elastic supporters 200 is less than 10centimeters per second. The area of the carbon nanotube film 100 can beincreased by stretching along D2.

Furthermore, in one embodiment, step (S10) can further include treatingthe carbon nanotube film 100 with organic solvent so that the apertures105 have larger width. The organic solvent can be volatile, such asethanol, methanol, acetone, dichloroethane, chloroform, or mixturesthereof. In one embodiment, the organic solvent is ethanol. The treatingthe carbon nanotube film 100 with organic solvent can be performed byapplying the organic solvent to entire surface of the carbon nanotubefilm 100 suspended on a frame or immersing the entire carbon nanotubefilm 100 with the frame in an organic solvent.

In one embodiment, the treating the carbon nanotube film 100 withorganic solvent includes soaking a suspended carbon nanotube film 100with an atomized organic solvent at least one time. In one embodiment,the soaking a suspended carbon nanotube film 100 can include steps of:providing a volatilizable organic solvent; atomizing the organic solventinto a plurality of dispersed organic droplets; and spraying the organicdroplets onto the surface of the suspended carbon nanotube film 100 andthe organic droplets gradually penetrating onto the carbon nanotubes ofthe carbon nanotube film 100, thereby making the suspended carbonnanotube film 100 be soaked at least one time by the organic droplets,and then make the carbon nanotube film shrink into a treated carbonnanotube film. The organic droplets are tiny organic solvent dropssuspended in surrounding. The organic solvent can be atomized into theorganic droplets by ultrasonic atomization method, high pressureatomizing method or other methods.

The organic solvent can be alcohol, methanol, acetone, acetic acid, andother volatilizable solvents. During the spraying process, a pressure isproduced, when the organic droplets are sprayed, the pressure is smalland can't break the carbon nanotube film 100. The diameter of eachorganic droplet is larger than or equal to 10 micrometers, or less thanor equal to 100 micrometers, such as about 20 micrometers, 50micrometers. Thus, an interface force is produced between the carbonnanotube film 100 and the organic droplets. The interface force canensure that the carbon nanotube film 100 is shrunk and the carbonnanotubes in the carbon nanotube film 100 are dispersed more uniformly.

The organic solvent is volatile and easy to be volatilized. When theorganic droplets are sprayed onto the carbon nanotube film 100 and thenpenetrated into the carbon nanotube film 100, the organic droplets arethen volatilized, and the carbon nanotube segments 108 loosely arrangedin the carbon nanotube film 100 are tightly shrunk. The diameter of eachorganic droplet is larger than or equal to 10 micrometers, or less thanor equal to 100 micrometers, the soaked scope of the carbon nanotubesegment of the carbon nanotube film 100 is limited by the small diameterof each organic droplet. Thus, diameters of the carbon nanotube segments108 of the carbon nanotube film 100 can be shrunk into less than orequal to 10 micrometers, the carbon nanotube segments 108 aresubstantially invisible using naked eyes in the treated carbon nanotubefilm. The carbon nanotube film 100 is original black or grey. However,after the soaking with an atomized organic solvent, the carbon nanotubefilm 100 is shrunk into the treated carbon nanotube film which is moretransparent.

In step (S20), the carbon nanotube film 100 can be suspended and treatedby oxidization or carbon accumulation to induce defects. The carbonnanotube film 100 not treated by inducing defects is defined as apristine carbon nanotube film 100. In one embodiment, part of the carbonnanotube film 100 is suspended by attaching on a frame and oxidized byoxygen plasma 300 treating.

In the process of treating the carbon nanotube film 100 by oxygen plasma300, the carbon nanotubes 104, 106 of the carbon nanotube film 100 areoxidized to form a plurality of dangling bond. In the process of oxygenplasma 300, the carbon nanotube film 100 can be connected to a power andhas an electric potential so that the carbon nanotube film 100 can bebombarded by the oxygen plasma 300 more strongly. When nano-materiallayer 110 are forming on the surface of the carbon nanotubes 104, 106 byatomic layer deposition, the atoms of the nano-material layer 110 canstack on the surface of the carbon nanotubes 104, 106 layer upon layerto form a compact nano-material layer 110 with high strength. Also, thethickness of the nano-material layer 110 is controllable so that anano-material layer 110 with a thickness in nano-scale can be obtained.In the process of oxygen plasma 300, the flow rate of the oxygen gas canbe in a range from about 30 sccm to about 60 sccm, the pressure of theoxygen gas can be in a range from about 8 Pa to about 12 Pa, thetreating time can be in a range from about 8 seconds to about 12seconds, and the treating power can be in a range from about 20 W toabout 30 W. In one embodiment, the flow rate of the oxygen gas is about50 sccm, the pressure of the oxygen gas is about 10 Pa, the treatingtime is about 10 seconds, and the treating power is about 25 W. As shownin FIGS. 9, 10A-10C, when the alumina layer has a thickness less than 30nanometers, the plurality of particles deposited on the pristine carbonnanotube film by atomic layer are discontinuous. When the alumina layerhas a thickness above 30 nanometers, the plurality of particlesdeposited on the pristine carbon nanotube film by atomic layer arejoined with each other to form a continuous alumina layer. However, lotsof junctions are formed between adjacent two of the plurality ofparticles. Furthermore, the alumina layer deposited on the pristinecarbon nanotube film by atomic layer has a smoothness at least above 10nanometers. As shown in FIGS. 11, 12A-12E, when the alumina layer has athickness less than 30 nanometers, the plurality of particles depositedon the oxygen plasma treated carbon nanotube film by atomic layer are acontinuous and uniform layer structure. Furthermore, the alumina layerdeposited on the oxygen plasma treated carbon nanotube film by atomiclayer has a smoothness at least less than 10 nanometers. In oneembodiment, the alumina layer deposited on the oxygen plasma treatedcarbon nanotube film by atomic layer has a smoothness less than 5nanometers. In one embodiment, the alumina layer deposited on the oxygenplasma treated carbon nanotube film by atomic layer has a smoothnessless than 3 nanometers even if the thickness of the alumina layer isless than 10 nanometers.

In the process of carbon accumulation, a carbon layer is coated on thesurface of the carbon nanotubes 104, 106. The method of carbonaccumulation can be physical vapor deposition (PVD), chemical vapordeposition (CVD), or spraying. In the process of carbon accumulation, anelectric current can be supplied to flow through the carbon nanotubefilm 100 to produce heat to heat the carbon nanotube film 100 itself. Inone embodiment, the carbon layer is coated on the surface of the carbonnanotubes 104, 106 by magnetron sputtering. In the magnetron sputtering,the current can be in a range from about 100 mA to about 200 mA, thepressure can be in a range from about 0.05 Pa to about 0.2 Pa, the flowrate of Ar can be in a range from about 5 Pa to about 15 sccm, and thesputtering time can be in a range from about 1.5 minutes to about 7.5minutes. In one embodiment, the current is about 150 mA, the pressure isabout 0.1 Pa, the flow rate of Ar is about 10 sccm, and the sputteringtime is about 5 minutes. As shown in FIG. 13, the carbon layer is coatedon the surface of the carbon nanotubes of the carbon nanotube film 100by magnetron sputtering.

The carbon layer includes a plurality of carbon particles to form thedefects on the surface of the carbon nanotubes 104, 106. Thus, whennano-material layer 110 are forming on the surface of the carbonnanotubes 104, 106 by atomic layer deposition, the atoms of thenano-material layer 110 can stack on the surface of the carbon nanotubes104, 106 layer upon layer to form a compact nano-material layer 110 withhigh strength. Also, the thickness of the nano-material layer 110 iscontrollable so that a nano-material layer 110 with a thickness innano-scale can be obtained. The thickness of the nano-material layer 110can be in a range from about 3 nanometers to about 30 nanometers. If thecarbon nanotube film 100 is not treated by carbon accumulation, thealumina layer deposited on the carbon nanotube film by atomic layerdeposition can form a continuous layer structure only at the thicknessabove 30 nanometers. If the thickness of the alumina layer deposited onthe carbon nanotube film by atomic layer deposition is smaller than 30nanometers, the alumina layer is a plurality of discontinuous particlesattached on the surface of the carbon nanotubes 104, 106. Thus, thealumina layer cannot form a compact layer structure. As shown in FIG.14, if the carbon nanotube film 100 is not treated with carbonaccumulation, the alumina layer deposited on the carbon nanotube film byatomic layer deposition is a plurality of discontinuous particles.However, as shown in FIG. 15, if the carbon nanotube film is treatedwith carbon accumulation, the alumina layer deposited on the carbonnanotube film by atomic layer deposition is a continuous layerstructure.

In step (S30), the source material of the atomic layer deposition can beselected according to the material of the nanotubes 112. For example,when the nanotubes 112 are metal oxide nanotubes 112, the sourcematerial of the atomic layer deposition includes metal organic compoundand water, and the carrier gas is nitrogen gas. The thickness of thenano-material layer 110 can be in a range from about 3 nanometers toabout 100 nanometers. In one embodiment, the thickness of thenano-material layer 110 is in a range from about 20 nanometers to about50 nanometers. The nano-material layer 110 can be coated on a surface ofa single carbon nanotube to form a continuous layer structure andenclose the single carbon nanotube therein. The nano-material layer 110can also be coated on a surface of two or more than two carbon nanotubesto form a continuous layer structure and enclose the two or more thantwo carbon nanotubes therein. The nano-material layer 110 can form aplurality of nanotubes 112 after the carbon nanotubes therein areremoved because the nano-material layer 110 is a compact continuouslayer structure. The plurality of nanotubes 112 can be combined witheach other to form a free-standing nanotube film 114. The nanotube 112can be a single linear nanotube or a branch nanotube. The material ofthe nano-material layer 110 can be metal oxide, metal nitride, metalcarbide, silicon oxide, silicon nitride, or silicon carbide.

In one embodiment, an alumina layer is deposited on the carbon nanotubefilm 100 by atomic layer deposition, the source materials of the atomiclayer deposition are trimethylaluminum and water, and the carrier gas isnitrogen gas. The alumina layer is deposited on the carbon nanotube film100 by following steps:

-   -   step (S301), suspending a portion of the carbon nanotube film        100 in a vacuum chamber of a atomic layer deposition device; and    -   step (S302), alternately introducing trimethylaluminum and water        in to the chamber of the atomic layer deposition device.

In step (S301), the carbon nanotube film 100 is attached on a frame sothat a portion of the carbon nanotube film 100 is suspended, and thenplaced into the vacuum chamber with the frame together. The frame can bea metal or ceramic frame. Because the carbon nanotube film 100 is freestanding, the carbon nanotube film 100 can be directly placed on twospaced supporters located in the vacuum chamber. When the elasticsupporters 200 mentioned above are made of thermostable material, thestretched carbon nanotube film 100 and the elastic supporters 200 can beplaced in the vacuum chamber together.

In step (S302), the carrier gas is nitrogen gas. The flow rate of thecarrier gas is about 5 sccm. The alternately introducingtrimethylaluminum and water includes following steps:

-   -   step (S3021), first evacuating the vacuum chamber to a pressure        of about 0.23 Torr;    -   step (S3022), introducing trimethylaluminum in to the vacuum        chamber until the pressure of the vacuum chamber rises to about        0.26 Torr;    -   step (S3023), second evacuating the vacuum chamber to the        pressure of about 0.23 Torr;    -   step (S3024), introducing water in to the vacuum chamber until        the pressure of the vacuum chamber rise to about 0.26 Torr;    -   step (S3025), third evacuating the vacuum chamber to the        pressure of about 0.23 Torr; and    -   step (S3026), repeating steps (S3022), (S3023), (S3024), (S3025)        to start another cycle.

In each cycle, the second evacuating the vacuum chamber to the pressureof about 0.23 Torr takes about 25 seconds, and the third evacuating thevacuum chamber to the pressure of about 0.23 Torr takes about 50seconds. The deposition velocity of the alumina layer is about 0.14nm/cycle. The thickness of the alumina layer can be controlled by thecycle number.

In step (S40), the carbon nanotube film 100 coated with nano-materiallayer 110 is annealed to remove the carbon nanotube film 100 and obtainthe plurality of nanotubes 112. The plurality of nanotubes 112 areorderly arranged and combined with each other to form the free-standingnanotube film 114. The annealing can be performed in oxygen atmosphereand at a temperature in a range from about 500° C. to about 1000° C. Inone embodiment, the carbon nanotube film 100 coated with nano-materiallayer 110 is suspended in a quartz tube filled with air and heated to550° C.

Referring to FIGS. 2 and 16, the single alumina nanotube film and thesingle carbon nanotube film have substantially the same structure.Referring to FIGS. 6 and 17, the two cross-stacked alumina nanotubefilms and the two cross-stacked carbon nanotube films have substantiallythe same structure. FIG. 18 shows that the alumina nanotube film is afree-standing nanotube film.

Referring to FIG. 19, the nanotube film 114 of includes a plurality ofnanotubes 112 orderly arranged and combined with each other. Thenanotube film 114 is a layer structure having two opposite surfaces inmacrocosm. In one embodiment, the plurality of nanotubes 112 arearranged to be substantially parallel with each other and extendsubstantially along the same direction. The plurality of nanotubes 112are spaced from each other or in direct contact with each other. Thelength of the nanotube 112 is not limited and can be the same as thelength of the carbon nanotube film 100 along the D1 direction. In oneembodiment, the length of the nanotube 112 is greater than 1 centimeter.

A plurality of openings 116 are defined by the plurality of spacednanotubes 112. The plurality of openings 116 extends through thenanotube film along the thickness direction. The plurality of openings116 can be a hole defined by several adjacent nanotubes 112, or a gapdefined by two substantially parallel nanotubes 112 and extending alongaxial direction of the nanotubes 112. The hole shaped openings 116 andthe gap shaped openings 116 can exist in the patterned nanotube film 114at the same time. The sizes of the openings 116 can be different. Theaverage size of the openings 116 can be in a range from about 10nanometers to about 500 micrometers. For example, the sizes of theopenings 116 can be about 50 nanometers, 100 nanometers, 500 nanometers,1 micrometer, 10 micrometers, 80 micrometers, or 120 micrometers. In oneembodiment, the sizes of the openings 116 are in a range from about 10nanometers to about 10 micrometers.

The adjacent nanotubes 112 are combined with each other by ionic bondsat the contacting surface and internal communicated. At least part ofthe plurality of nanotubes 112 extend from a first side of the nanotubefilm 114 to a second side opposite to the first side. The majority ofnanotubes 112 of the nanotube film 114 are arranged to substantiallyextend along the same direction and in parallel with the surface of thenanotube film 114. A minority of dispersed nanotubes 112 of the nanotubefilm 114 may be arranged randomly, crossed with and in direct contactwith the adjacent nanotubes 112. Thus, the nanotube film 114 is afree-standing structure.

Referring to FIG. 20, the nanotube 112 includes a cylinder shaped cell1122. The cylinder shaped cell 1122 defines a cylinder shaped space1124. The thickness of the wall of the cylinder shaped cell 1122 can bein a range from about 3 nanometers to about 100 nanometers. The insidediameter of the cylinder shaped cell 1122 can be in a range from about10 nanometers to about 100 nanometers. The material of the nanotube 112can be metal oxide, metal nitride, metal carbide, silicon oxide, siliconnitride, or silicon carbide. In one embodiment, the nanotube 112 is analumina nanotube with a thickness of about 30 nanometers and an insidediameter of about 20 nanometers.

As shown in FIG. 21, two nanotube films 114 can be stacked with eachother. The extending directions of nanotubes 112 in the two stackednanotube films 114 form an angle α in a range from about 0° to about90°. In one embodiment, the extending directions of nanotubes 112 in thetwo stacked nanotube films 114 are substantially perpendicular with eachother so that the two stacked nanotube films 114 defines a plurality ofopenings 116. The two stacked nanotube films 114 are combined with eachother by ionic bonds to form a free standing structure with improvedstrength.

As shown in FIG. 22, a mechanical strength of a first cross-stackedalumina nanotube film made by template of a carbon nanotube film treatedwith oxygen plasma is tested. The first cross-stacked alumina nanotubefilm can bear a load of about 0.06 N. As shown in FIGS. 22-23, amechanical strength of a second cross-stacked alumina nanotube film madeby template of a pristine carbon nanotube film is tested. The secondcross-stacked alumina nanotube film can bear a load of about 0.029 Nthat is greater than a greatest stretching force two stacked carbonnanotube film can bear. The first cross-stacked alumina nanotube film ismuch stronger than that of the second cross-stacked alumina nanotubefilm. Because the pristine carbon nanotube film is lack of active sitesfor alumina nanoparticles to grow on carbon nanotubes, with increasingthe number of ALD cycles, although the alumina nanoparticles grow biggerand coalesce gradually to form tubular structure, a plurality ofjunctions are also formed as show in FIGS. 10A-10C. These junctions inthe alumina nanotube film serve as the weak joints and thus affect themechanical strength seriously.

Furthermore, because the carbon nanotube film is drawn from supperaligned carbon nanotube array and includes a plurality of joints betweenadjacent two carbon nanotubes, adjacent two carbon nanotubes are joinedonly by van der Waals force. Thus, the strength of the carbon nanotubefilm is relatively weak. The second cross-stacked alumina nanotube filmis made using the two stacked carbon nanotube film as a template,adjacent two nanotubes are joined by ionic bonds. Thus, the secondcross-stacked alumina nanotube film has a relative high strength thanthat of the two stacked carbon nanotube films.

The embodiments shown and described above are only examples. Even thoughnumerous characteristics and advantages of the present technology havebeen set forth in the foregoing description, together with details ofthe structure and function of the present disclosure, the disclosure isillustrative only, and changes may be made in the detail, including inmatters of shape, size and arrangement of the parts within theprinciples of the present disclosure up to, and including, the fullextent established by the broad general meaning of the terms used in theclaims.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. The description and the claims drawn to a method may includesome indication in reference to certain steps. However, the indicationused is only to be viewed for identification purposes and not as asuggestion as to an order for the steps.

What is claimed is:
 1. A nanotube film structure comprising: a nanotubefilm, wherein the nanotube film comprises a plurality of nanotubesorderly arranged and ionicly bonded to each other by direct contact witheach other, and the nanotube film is free of carbon nanotubes.
 2. Thenanotube film structure of claim 1, wherein adjacent two of theplurality of nanotubes are internally communicated such that interior ofthe adjacent two of the plurality of nanotubes are in communication witheach other at a location where the adjacent two of the plurality ofnanotubes are in direct contact with each other.
 3. The nanotube filmstructure of claim 1, wherein the plurality of nanotubes aresubstantially parallel with each other.
 4. The nanotube film structureof claim 3, wherein the nanotube film comprises two stacked nanotubefilms.
 5. The nanotube film structure of claim 4, wherein nanotubes ofone of the two stacked nanotube films are perpendicular with nanotubesof the other one of the two stacked nanotube films.
 6. The nanotube filmstructure of claim 4, wherein the two stacked nanotube films arecombined with each other by ionic bonds.
 7. The nanotube film structureof claim 1, wherein each of the plurality of nanotubes has a wall with athickness in a range from about 10 nanometers to about 100 nanometers.8. The nanotube film structure of claim 1, wherein at least part of theplurality of nanotubes extend from a first side of the nanotube film toa second side opposite to the first side.
 9. The nanotube film structureof claim 1, wherein a length of the plurality of nanotubes is the sameas a length or a width of the nanotube film.
 10. The nanotube filmstructure of claim 1, wherein a material of the plurality of nanotubesis selected from the group consisting of metal oxide, metal nitride,metal carbide, silicon oxide, silicon nitride and silicon carbide. 11.The nanotube film structure of claim 1, wherein the nanotube filmdefines a plurality of openings.
 12. The nanotube film structure ofclaim 1, wherein the nanotube film is a free-standing structure.
 13. Ananotube film structure comprising: a nanotube film, wherein thenanotube film comprises a plurality of nanotubes ironically bonded toeach other by direct contact with each other and fabricated from amaterial selected from the group consisting of metal oxide, metalnitride, metal carbide, silicon oxide, silicon nitride and siliconcarbide, and the nanotube film is free of carbon nanotubes.
 14. Thenanotube film structure of claim 13, wherein the nanotube film is afree-standing structure.